1. Field of the Invention
This invention relates generally to the field of private branch exchange telecommunication systems and, more particularly, to a private branch exchange system having various call servicing features for calls terminating at private branch exchange telephonic units of the system.
2.Description of the Prior Art
Telecommunication systems having a private branch exchange (PBX) controlled by a central control processing unit in conjunction with a main memory for connecting telephonic calls received from external telephonic units of an external switching network with private branch exchange telephonic units at predetermined positions of the PBX are well known. Examples of such systems are shown in U.S. Pat. No. 5,268,903 of Jones et al. entitled "Multichannel Telephonic Switching Network With Different Signaling Formats and Cross Connect/PBX Treatment Selectable For Each Channel", issued Dec. 7, 1993; U.S. Pat. No. 5,140,611 of Jones et al. entitled "Pulse Width Modulated Self-Clocking and Self-Synchronizing Data Transmission and Method for a Telephonic Communication Network Switching System", issued Aug. 18, 1992; U.S. Pat. No. 5,127,004 of Lenihan et al. entitled "Tone and Announcement Message Code Generator for a Telephonic Switching System and Method" issued Jun. 30, 1992 and U.S. Pat. No. 4,627,047 of Pitroda et al. entitled "Integrated Voice and Data Telecommunication Switching System", issued Dec. 2, 1986.
In PBX systems, telephonic calls are switched to a particular line identified by the dialed call and connected to a PBX telephonic unit associated with the telephone line. Unlike, in automatic call distributor systems in which calls are routed to various groups or pools of agents for servicing, PBX systems are programmed to route a received call directly to the PBX position or PBX telephonic unit identified by the call dialed from the calling party. A call terminating at a PBX position telephonic unit that is busy or is set not to accept calls, is handled by one or more different call servicing features (e.g. call forwarding, subsequent call back, forward to voice mail, etc.) of the PBX system. The feature types and the order of the procedural steps for handling a PBX call directed at an associated PBX position telephonic unit are based on programmed and stored `C` code in known PBX systems. The order in which the terminating features for a call associated with a particular PBX position are checked by the system against any feature specific decisions about call handling residing in the compiled and stored software code.
The compiled code checks the current state of a call along with provisionable feature parameters to implement decisions on call handling. Therefore, PBX systems operate according to the fixed internal software feature ordering. Disadvantageously, the stored and compiled code is not readily alterable without the necessity of employing a skilled programmer who must accurately reprogram the system to the desired change in feature ordering without interfering with the internal operation of the system.
In certain automatic call distribution systems various call handling features or applications associated with particular agent groups are alterable by the user without reprogramming the compiled code internally stored at the call distributor. This type of alterable call feature handling in an automatic call distributor is seen in U.S. patent application Ser. No. 07/975,240 of Sumner et al. entitled "Control Device For The Network Of A Telephone Switching System" filed Nov. 12, 1992. Unfortunately, the user alterable call feature handling for automatic call distributors is not seen in PBX systems. Moreover, the operation of a PBX system significantly differs from that of an automatic call distributor. Automatic call distributions are very structured for the specific purpose of routing calls to agent groups for servicing a high volume of calls in a short time. Agent consoles in automatic call distributors are generally limited to application features relating to optimizing the agent handling of a call by minimizing the discrete actions required to answer and process a call. In automatic call distribution systems, calls are routed to agent groups with the corresponding agents having very little or no control in the method of routing or of answering received calls. A PBX position telephonic unit, conversely, is a general purpose device having call handling features which enable the called party to either answer a call or send the call to alternate destinations (e.g. voice mail). However, in known PBX systems, a fixed order of operation is set in the compiled code for calls associated with a PBX position. The user or system administrator has no control over the execution of PBX calls since the PBX system operates only according to its internal software feature ordering. Once a particular order of feature operation is determined, in known systems, the set operation is fixed in compiled code software modules internal to the system. Disadvantageously, an operational change in the features for PBX positions, in a known system, requires the extremely time consuming and highly skilled task of reprogramming the internally stored compiled feature application software code. Therefore, even the slightest modification to feature operations are time consuming, inefficient and costly to the user due to the inflexibility of known PBX systems.